AD698

REV. B

–11–

2

× R

S









×V

IN

Ω then:

× R

Ω

Choose an oscillator amplitude that is in the range of 1 V to

3.5 V rms. For an input excitation level of 3 V rms, the output

signal from the amplifier gain stage will be 3.5 V rms

× 0.8 V or

2.4 V rms, which is in the acceptable range.

Since A/B is known, the value of R2, the output FS resistor may

be chosen by the formula:

For a 10 V output at FS, with an A/B of 0.8; solve for R2.

R2 = 10 V [0.8

× 500 µA] = 25.0 kΩ

bridge. The other components, C1, C2, C3, C4 may be selected

by following the guidelines on general device operation men-

tioned earlier.

If a gain trim is required, then a trim resistor can be used to ad-

network on the OFFSET 1 and OFFSET 2 pins of the AD698.

R1

C1

C2

C3

R4

R3

C4

R2

1000pF

SIGNAL

REFERENCE

100nF

6.8µF

–15V

+15V

100nF

6.8µF

AB

C

D

PHASE

LAG/LEAD

NETWORK

13

16

15

14

24

23

22

21

20

19

18

17

12

11

10

9

8

1

2

3

4

7

6

5

AD698

EXC1

EXC2

LEV1

LEV2

FREQ1

BFILT1

BFILT2

–BIN

+BIN

–AIN

FREQ2

SIG REF

OFFSET2

OFFSET1

OUT FILT

FEEDBACK

SIG OUT

–ACOMP

AFILT2

AFILT1

+ACOMP

+AIN

A2

A1

RESISTORS,

INDUCTORS

OR CAPACITORS

AB

CD

PHASE LEAD

C

C

A

B

CD

PHASE LAG

C

PHASE LAG = Arc Tan (Hz RC);

PHASE LEAD = Arc Tan 1/(Hz RC)

DUAL

OP AMP

Figure 20. AD698 Interconnection Diagram for AC Bridge Applications